Background: Barrett's esophagus (BE) is the precursor lesion for esophageal adenocarcinoma. While there is information on isolated somatic changes that occur during the progression of BE to dysplasia or cancer, the global changes in somatic gene expression underlying the transformation of normal esophageal mucosa to BE remain unknown. Hypothesis: BE is associated with altered gene expression patterns. Comparative gene expression studies using microarray analyses would identify BE-specific genes that provide insight into the molecular basis of BE. Our preliminary data indicate an overactive Wnt/beta-catenin pathway in BE. Specific Aim #1: To identify the specific gene expression pattern for Barrett's esophagus. a) Recruit individuals from three well-defined phenotypically distinct cohorts: patients with BE, patients with GERD and no BE, and volunteers with no GERD or BE. b) Obtain endoscopically and histologically well-defined tissue classes from cohorts identified in SA#1.a.; these tissue classes are BE, normal esophageal, gastric, duodenal, and colonic epithelia. c) Use laser microdissection to capture glandular tissue. d) Use microarray analysis to compare the global gene expression of BE to several control tissues obtained from the three cohorts (SA# 1.a and 1.b). Specific Aim #2: To identify novel gene(s) and/or pathways in the pathogenesis of Barrett's esophagus. a) Apply the gene expression data to metabolic and/or physiological pathways with sample size calculation geered toward the Wnt/beta-catenin pathway. b) Use quantitative RT-PCR to confirm the altered expression of BE-specific genes. Methods: We will obtain endoscopic biopsies from esophageal, gastric, duodenal, and colonic tissue from 30 patients (10 with BE, 10 with GERD w/o BE, and 10 with no GERD or BE). We will conduct microarray assays using RNA extracted from these specimens on Human Genome Affymetrix (HG- 133U) Set GeneChip(r). The data will be analyzed to identify downregulated and upregulated genes that are unique to BE. Pathway surveys will be conducted with confirmation of these genes using RT-Q-PCR. We present preliminary data on microarray and RT-PCRanalyses on 5 patients with BE that suggest an overactive Wnt pathway: we have also assembled the essential components of a successful study using microarrays.